One of the hardest questions in retirement planning is deceptively simple: how much can you take out of your investment portfolio each year without running out of money? Spend too little and you may deny yourself a retirement you could have comfortably afforded. Spend too much, especially in the early years, and a bad market could leave you with nothing in your eighties.
The most famous attempt to answer this question is the 4% rule — a rule of thumb that has shaped retirement planning for three decades. Alongside it sits a slightly more generous cousin, often called the 5% rule, which trades safety for simplicity and higher income. This article explains where these rules come from, what assumptions sit behind them, and how to adapt them to your own circumstances as a long-term European investor.
What is the 4% rule?
The 4% rule refers to withdrawing 4% of a retirement portfolio in the first year of retirement, then increasing that withdrawal each year with the consumer price index (CPI) so your spending keeps pace with the cost of living. Crucially, the percentage applies only to year one. After that, you withdraw the same inflation-adjusted amount regardless of what the market is doing.
A concrete example. Suppose you retire with a portfolio whose annual expenses equal exactly 4% of its value. In year one you withdraw that 4% amount. If inflation is 3% that year, your year-two withdrawal is your year-one amount increased by 3% — not 4% of whatever the portfolio is then worth. The portfolio itself may have risen or fallen over the year; your withdrawal stays anchored to your cost of living.
The rule assumes the portfolio must last 30 years — a typical planning horizon for someone retiring in their mid-sixties. It also implies a savings target: you need 25 times your annual expenses, because 100% ÷ 4% = 25. That is why you will often see retirement targets expressed as a multiple of annual expenses — 25× for the 4% rule, or 20× for a 5% starting rate.
Where the rule comes from
The 4% rule was developed by Bill Bengen, a US financial planner, in 1994. His paper, "Determining Withdrawal Rates Using Historical Data," asked a practical question: what is the highest withdrawal rate that would have survived every retirement in modern market history? Using rolling 30-year periods built from monthly data since January 1926 — covering large-company stocks and intermediate-term government bonds — he tested each historical retirement against the worst sequences the markets had ever delivered.
Four years later, three finance professors at Trinity University published what became known as the Trinity study, backtesting a wide range of stock/bond mixes and withdrawal rates against market data covering 1925 to 1995. Their conclusion was striking: "withdrawal rates of 3% to 4% continue to produce high portfolio success rates for stock-dominated portfolios," and 3% and 4% level payouts are "extremely unlikely to exhaust any portfolio of stocks and bonds."
The logic of the method is worth understanding. The researchers did not forecast the future. Instead, they replayed history: a person retiring in 1930, 1950, 1966, and so on, each following the same withdrawal rule, and checked whether the money lasted 30 years in every case. The rule that survived the worst historical outcome became the "safe" rate.
Why 4% and not more
It is tempting to reason as follows: if a diversified portfolio earns roughly 7% a year after inflation over the long run, why not simply withdraw 7% and live on the average return? The answer is sequence-of-returns risk — the fact that when returns arrive matters as much as their average.
Averaging only works if your portfolio is untouched. Once you are withdrawing money, a market crash early in retirement is far more damaging than the same crash later. If your portfolio falls 30% in year two and you still withdraw your full inflation-adjusted amount, you are selling assets at depressed prices and digging a hole that is increasingly difficult to climb out of, even when a recovery arrives. The same crash in year twenty-five, when most of the withdrawals are already behind you, barely matters.
Bengen captured this with his concept of the SAFEMAX: the highest sustainable inflation-adjusted withdrawal rate for the worst-case historical retirement. In his original research, that figure was 4.15% for a portfolio split evenly between stocks and bonds — and the worst-case scenario was not the Great Depression but the retirement cohort beginning in 1966, which was hit by poor returns and high inflation in its early years. Bengen also recommended that retirees maintain a substantial stock allocation, writing that clients should accept "a stock allocation as close to 75 percent as possible, and in no cases less than 50 percent." Without growth, the withdrawals themselves would erode the portfolio.
It's a guideline, not a guarantee
It is essential to understand what the 4% rule is and is not. It is a historical backtest — a statement about what would have worked in past American markets. It is not a law of finance, and the researchers themselves were careful on this point. The Trinity study authors emphasised that "selection of a withdrawal rate is not a matter of contract but rather a matter of planning," warning that mid-course corrections will likely be required.
Several caveats follow from this:
- The future may differ from the past. Return patterns, inflation and longevity all evolve. A rate that survived every 30-year period since 1926 offers no promise about the next 30 years.
- The rule assumes fixed spending. Critics have pointed out, as one 2008 analysis did, that the 4% rule finances "a constant, non-volatile spending plan using a risky, volatile investment strategy" — producing unspent surpluses in good markets and spending shortfalls in bad ones. Real households rarely spend that way.
- Emergencies happen. Research by Pye in 2010 found that accounting for the chance of costly emergencies each year reduces a sustainable withdrawal from 4% to about 3%. A roof replacement or a family crisis is not in the model.
- Monitoring is part of the plan. The rule works only if you track your portfolio and adjust when reality diverges from the assumptions — a discipline closely related to tracking portfolio performance and rebalancing your portfolio.
More conservative and flexible alternatives
Because the historical 4% figure rests on past data, more recent research has taken a forward-looking approach. Morningstar's 2021 study used forecasts of future returns rather than historical averages and estimated a 3.3% safe starting withdrawal rate for a balanced portfolio with fixed real withdrawals over 30 years and a 90% probability of success. Its estimates have moved with market conditions since, as the table below shows.
The swings in these estimates are themselves instructive: the "safe" rate depends on the returns and inflation expected at the time of the analysis, not on a fixed constant of nature.
Flexibility, rather than a lower fixed number, is the other main response. Morningstar's research evaluates several flexible strategies:
- Skipping inflation raises after loss years. If your portfolio fell over the past year, you hold your withdrawal flat instead of increasing it for inflation, letting the portfolio recover.
- Guardrails. You set upper and lower bounds on your withdrawal rate. In down markets you take less; in strong markets you may take a little more. Spending flexes with the portfolio instead of fighting it.
- Fixed-percentage withdrawals. You take a fixed percentage of the current portfolio value each year — say 4% or 5% of whatever it is worth. The income fluctuates, but the portfolio can never be fully depleted, because you never withdraw more than a set share of what remains.
The trade-off is clear: flexibility means your income is less predictable, but your portfolio is far more resilient. For many retirees, a hybrid — a base withdrawal with modest cuts after bad years — captures most of the benefit.
Adapting the rule to your situation
The 4% rule assumes your portfolio is your only income source. In practice, most European retirees have more. A Romanian retiree, for example, may receive a state pension, and may also draw on private pension pillar payouts. Every euro of reliable income from these sources reduces what the portfolio must cover — and therefore reduces the multiple of expenses you need to save.
Suppose part of your total retirement spending is covered by a state pension. Your portfolio only needs to fund the remainder, so at a 4% starting rate you need 25 times that remainder rather than 25 times your full spending. Other income — rental property, part-time work, a defined-benefit payout — works the same way, and supplemental income in weak market years can substitute for portfolio withdrawals precisely when selling assets would be most costly.
Retirement length matters too. The 30-year horizon behind the classic rule suits someone retiring at 65. Retiring at 50 means the money may need to last 40 years or more, which argues for a more conservative starting rate or a more flexible spending plan — a consideration central to financial independence planning. Your asset mix matters as well; Bengen's figures assume a stock allocation of at least 50%, so a portfolio heavy in cash or bonds behaves differently. Useful background for that decision can be found in what is asset allocation? and asset allocation by age.
The overall decision can be visualised like this:
Key takeaways
- The 4% rule means withdrawing 4% of your portfolio in year one of retirement, then raising that amount with inflation each year, assuming a 30-year horizon. It implies a target of 25× annual expenses.
- The rule comes from Bengen's 1994 research and the 1998 Trinity study, which backtested withdrawal rates against market data going back to the mid-1920s. Bengen's worst-case sustainable rate was 4.15% for a 50/50 portfolio.
- You cannot simply withdraw the average return: sequence-of-returns risk means early losses combined with withdrawals can permanently damage a portfolio.
- The rule is a planning guideline, not a contract. Forward-looking estimates have ranged from 3.3% to 4.0% in recent years, and real-life emergencies can push the sustainable rate lower.
- Flexible strategies — skipping inflation raises after loss years, using guardrails, or withdrawing a fixed percentage of the remaining portfolio — trade income predictability for greater resilience.
- Combine portfolio withdrawals with state and private pension income, adjust for your expected retirement length, and review your plan annually with a willingness to make mid-course corrections.
Educational only — not personalised investment advice.